The human heart is about the size of a first and weighs less than a pound. It is located in a cavity of the thorax called the mediastinum and is covered by the pericardium, a double sac of membranes that releases fluids to lubricate the heart and reduce friction. The three layers of the heart (as shown in the image below) are the epicardium which is the visceral pericardium, the myocardium which is the contractile part of the heart, and the endocardium which lines the chambers of the heart.
The heart has four chambers that help regulate the blood: the right and left atria, which receive blood, and the right and left ventricles, which discharge blood. The valves of the heart - labelled in the image below - keep blood moving in one direction and prevent the back flow of blood. When listening to a heart beat, the "lub" sound happens when the tricuspid valve (between the right atrium and right ventricle) and the bicuspid valve (between the left atrium and left ventricle) contract. The "dub" sound is heard when the aortic and pulmonary valves close as the heart relaxes. The nodal system of the heart is composed of the SA (sinoatrial) node which is found in the right atrium and the AV (artrioventricular) node which is found where the atria and ventricles meet. This nodal system is made up of special tissue that causes the heart to beat uniformly at about 75 beats per minute. The cardiac cycle is the heat's rotation between systole (contraction) and diastole (relaxation) of both the atria and both the ventricles that work together to push blood through the body. For more information on how blood is circulated through the chambers of the heart, see my previous blog post from our heart chalk walk activity here
The circulatory system is a fluid-filled network of vessels through which materials move between the environment and cells of a multicellular animal. It's major components are the heart which continuously circulates blood, the arteries which take blood away from the heart, the veins which bring blood back to the heart, and blood which is the fluid being circulated. The image below depicts the structural differences between arteries and veins. The specific parts of the circulatory system are pulmonary veins and arteries, the aortic arch and trunk, the common carotid artery, the renal vein and artery, and the mesenteric arteries. Some accessory organs that aid in the circulation of blood are the lungs, kidneys, small intestine, large intestine, liver, spleen, and bone marrow. Blood pressure is measured by the systolic pressure, which results from the contraction of the ventricles, and diastolic pressure from the relaxation of the heart. To learn more about blood pressure, see my last blog post from our blood pressure lab here
Many blood vessels work together to aid in the circulation of blood through the circulatory system as shown in the diagram above. Veins are thin vessels that carry blood from the tissues to the heart. Arteries are elastic and contractile vessels that carry blood away from the heart and to the tissues. Capillaries are tiny vessels that connect arterioles (small arteries) to venules (small veins). Blood - the main material pumped through the circulatory system - has three components (depicted below): red blood cells, a buffy coat made up of white blood cells and platelets, and plasma. Blood's main functions are transportation, regulation, and protection. Different types of white blood cells in peripheral blood include neutrophils, basophils, eosinophils, lymphocytes, and monocytes, each of which has different responsibilities in the body.
One of the main cardiovascular diseases is a heart attack, which is caused when blood supply to the myocardium is severely reduced or blocked and is usually due to atherosclerosis. Atherosclerosis is a disease that occurs when fatty material deposits on the inside of blood vessels, making it harder for blood to flow - the chronic inflammation is generally caused by excess polyunsaturated fats, omega-6, and damaged blood vessels that cause LDL (bad cholesterol) to stick to damaged cells causing plaque to develop, as shown in the image below. Another cardiovascular injury, an aneurysm occurs when a thin weakened portion of the blood vessel wall droops, and they are life threatening, especially if they burst. Cholesterol, a cause of atherosclerosis, comes in two types: LDL which sticks to arteries and HDL which cleans up the build up of LDL in arteries. A major effect of a heart attack which is often confused with a heart attack is cardiac arrest, which occurs when the heart stops beating entirely. Signs of a heart attack include chest pain/pressure, arm pain, nausea, shortness of breath, and pale/sweaty skin. Methods to diagnose a cardiovascular disease include an angiogram, an echocardiogram, an electrocardiogram (EKG/ECG), a stress test, or nuclear scanning. Factors that increase the risk of a heart attack are a lack of exercise, obesity, smoking, diabetes, high blood pressure, and high cholesterol. Thus, it's important to maintain good health to prevent a heart attack from occurring.
No comments:
Post a Comment